1. Field of the Invention
The present invention relates to a method for preparing chamfering data necessary for chamfering a peripheral edge of a spectacle lens with use of a chamfering grinding wheel, a spectacle lens chamfering method, a spectacle lens chamfering data preparing apparatus, and a spectacle lens chamfering apparatus.
2. Description of the Prior Art
Heretofore, as chamfering apparatuses there have been known, for example, such lens grinding apparatuses as disclosed in Japanese Patent Laid Open Nos. 225853/1998, 225854/1998 and 225855/1998.
In these known lens grinding apparatuses, as shown in FIG. 11, a peripheral edge portion MLs of a base lens MLxe2x80x2 is subjected to grinding to form a V-shaped protrusion MLy and thereafter it is possible to form chamfered portions MLmf and MLmr (which will be referred to as V shoulders) at both sides of the V-shaped protrusion V shoulders Hf and Hr of the resulting spectacle lens ML. The chamfered portion MLmr is formed at a position closer to a rear refraction plane MLr than the V-shaped protrusion MLy, while the chamfered portion MLmf is formed at a position closer to a front refraction plane MLf than the V-shaped protrusion MLy.
For example, the chamfered portion MLmr is formed by dividing a V shoulder width Hr (thickness of the V-shaped protrusion bottom) of the rear refraction plane MLr at a predetermined ratio Hr1:Hr2 and by chamfering the peripheral edge portion of the spectacle lens ML throughout the whole circumference while maintaining the above dividing ratio.
Likewise, the chamfered portion MLmf is formed by dividing a V shoulder width Hf (thickness of the V-shaped protrusion bottom) of the front refraction plane MLf at a predetermined dividing ratio Hf1:Hf2 and by chamfering the peripheral edge portion of the spectacle lens ML throughout the whole circumference while maintaining the dividing ratio.
It is also possible to divide an edge thickness Wi (at Wif:Wir ratio) with the apex of the V-shaped protrusion MLy as a boundary, then to chamfer the whole circumference of the spectacle lens ML with the V shoulder ratio Hf1, Hf2 and the ratio Hr1, Hr2 while maintaining the dividing ratio (Wif:Wir).
More specifically, the chamfered portion MLmr can be formed by dividing the V shoulder at a ratio of Hr1:Hr2=4:6 and chamfering the spectacle lens ML throughout the whole circumference while maintaining this dividing ratio.
Such a chamfering work is applied, for example, when the spectacle lens ML is increased, for example, due to an increase in the dioptric power of the spectacle lens ML. In this case, the distance from the lens center to lens edge end is longer on the ear-contacting side than the distance between the upper edge to the center, so the edge thickness is larger on the ear-contacting side. For this, conventionally, chamfering of the lens edge is performed in such a manner that a chamfering quantity (MLmf and MLmr) is larger at the ear-contacting side so that the edge thickness Wi appears thinner when the spectacle is worn.
Besides, the spectacle lens edge, i.e., the peripheral edge portion of the spectacle lens ML is fitted in a spectacle frame or the like. Accordingly, when the spectacle lens edge is chamfered to a degree such that the edge thickness Wi of the spectacle lens ML is slightly thicker than the rim thickness of the spectacle frame, the spectacle lenses can fit the taste of a person who wears the spectacle.
In the case where the thus-chamfered spectacle lens ML is fitted in a spectacle frame and the spectacle is worn by a user, it is not a sideways chamfered shape but a chamfered shape as seen from the front side that actually attracts attention of another person. That is, the portions which actually attract attention in the spectacle lens ML are the entire shapes of the chamfered portions MLmf and MLmr formed on the front and the rear refraction planes MLf, MLr, respectively, of the spectacle lens ML.
However, when the chamfered spectacle lens ML is seen from the front side, if the entire shapes of the chamfered portions MLmf and MLmr after chamfering do not draw beautiful curves along the rim of the spectacle frame, it cannot be said that the chamfering is successful.
It should be noted that there is no problem of the chamfered portions MLmf and MLmr when the right and left lenses have an identical dioptric power and an identical lens thickness and the frame shape is basically symmetrical in right and left direction. However, when a user of a spectacle has eyes of different refraction powers, the base lens MLxe2x80x2 used for the right and left eyes also differ in thickness. That is, when the right and left eye-glasses have different dioptric powers, with the foregoing simple ratio (Hr1:Hr2 or Wif:Wir) will result in that the chamfer width Hmr of the chamfered portion MLmr formed on the rear refraction plane MLr differs greatly between the right and left spectacle lenses ML. This is not desirable because the spectacle frame looks different in shape on the right and left sides thereof in appearance. In other words, it is preferred for the spectacle frame not to be seen different in shape on the right and lefts sides thereof in appearance. Accordingly, when using right and left base lenses MLxe2x80x2 of different dioptric powers, if it is preferable that right and left chamfered portions MLmr are almost equal to each other (symmetry right and left).
It is therefore an object of the present invention to provide a spectacle lens chamfering data creation method, a spectacle lens chamfering method, a spectacle lens chamfering data creation apparatus, and a spectacle lens chamfering apparatus which are capable of chamfering viewed from the front or rear surface of the spectacle lens, chamfering preferable for a user of the spectacle, collecting lens edge shape data along the chamfering locus, and chamfering based on the collected data.
For achieving the aforementioned object, the present invention provides a spectacle lens chamfering data creation method comprising steps of: entering spectacle frame lens shape information and a predetermined chamfer width; and calculating a chamfer locus on a refraction plane of a spectacle lens having the lens shape obtained by using the lens shape information.
According to another aspect of the present invention, the spectacle lens chamfering data creation method comprises steps of: entering spectacle frame lens shape information and a predetermined chamfer width; and obtaining data on a lens edge/shape along a chamfer locus on a refraction plane of a spectacle lens having the lens shape obtained by using the lens shape information.
According to still another aspect of the present invention, the spectacle lens chamfering data creation method comprising steps of: entering spectacle frame lens shape information and a reference chamfer width at a radius vector at a predetermined angle of the lens shape information; entering a minimum chamfer width at a radius vector at another angle of the lens shape information; and obtaining a chamfer locus on a refraction plane of a spectacle lens by using a position of the reference chamfer as one reference and a position of the minimum chamfer as another reference.
According to yet another aspect of the present invention, the spectacle lens chamfering data creation method comprises steps of: entering spectacle frame lens shape information and a reference chamfer width at a radius vector at a predetermined angle of the lens shape information; entering a minimum chamfer width at a radius vector at another angle of the lens shape information; obtaining a chamfer locus on a refraction plane of a spectacle lens by using a position of the reference chamfer as one reference and a position of the minimum chamfer as another reference; and obtaining data on a spectacle lens edge thickness/shape along the chamfer locus.
According to yet still another aspect of the present invention, chamfer width values at several points of the spectacle lens shape (periphery) are entered to obtain the chamfer locus according to the chamfer width values at the respective points.
According to still yet another aspect of the present invention, the spectacle lens chamfering method comprises steps of: obtaining a chamfer locus by using the aforementioned spectacle lens chamfering data creation method; calculating a spectacle lens edge thickness along the obtained chamfer locus; and performing chamfering.
In one aspect of the apparatus for preparing spectacle lens chamfering data according to the present invention, the apparatus comprises a lens shape data input means for inputting lens shape data of a spectacle frame, a chamfer width input means for inputting a predetermined chamfer width from a peripheral edge of the inputted lens shape, and a computing means for determining a chamfer locus on a refraction plane of a spectacle lens from the inputted chamfer width.
In another aspect of the apparatus for preparing spectacle lens chamfering data, the apparatus comprises a lens shape data input means for inputting lens shape data of a spectacle frame, a chamfer width input means for inputting a predetermined chamfer width from a peripheral edge of the inputted lens shape, a computing means for determining a chamfer locus on a refraction plane of a spectacle lens from the inputted chamfer width, and an edge thickness shape data input means for inputting edge thickness shape data of the spectacle lens along the chamfer locus thus determined.
In a further aspect of the apparatus for preparing spectacle lens chamfering data, the apparatus comprises a lens shape data input means for inputting lens shape data of a spectacle frame, a chamfer width input means for inputting a chamfer width of a reference chamfer from a first peripheral edge of the inputted lens shape and inputting a chamfer width of a minimum chamfer from a second peripheral edge of the lens shape in another meridian direction, and a computing means for determining a chamfer locus on a refraction plane of a spectacle lens with a chamfer end position of the reference chamfer and that of the minimum chamfer as a reference.
In a still further aspect of the apparatus for preparing spectacle lens chamfering data, the apparatus comprises a lens shape data input means for inputting lens shape data of a spectacle frame, a chamfer width input means for inputting a chamfer width of a reference chamfer from a first peripheral edge of the inputted lens shape and inputting a chamfer width of a minimum chamfer from a second peripheral edge of the lens shape in another meridian direction, a computing means for determining a chamfer locus on a refraction plane of a spectacle lens with a chamfer end position of the reference chamfer and that of the minimum chamfer as a reference, and an edge thickness shape data input means for inputting edge thickness shape data of the spectacle lens along the chamfer locus.
In a still further aspect of the apparatus for preparing spectacle lens chamfering data, in combination with any of the above apparatus, the chamfer width input means inputs a chamfer width in a normal line direction from each of peripheral edge points of the lens shape of the spectacle frame, and the computing means determines a chamfer locus with a chamfer end position at each of the peripheral edge points as a reference.
Further, in one aspect of the apparatus for chamfering a spectacle lens according to the present invention, the apparatus comprises a chamfering wheel for chamfering a spectacle lens on the basis of edge thickness shape data of the spectacle lens obtained along a chamfer locus, the chamfer locus being obtained using any of the above spectacle lens chamfering data preparing apparatuses.